ComputerAndVideoGames.com has tossed up a review of Legends of Aranna, giving the Dungeon Siege expansion an overall score of 78/100. A snippet:

The new landscapes are as pretty and detailed as the old, the combat is still hectic but very smooth, and with the lack of any real Dungeon Siege total conversions, Legends has come along at just the right time.

The only real disappointment if you've completed the main campaign is there's no way to import your high-level character into the expansion, which means you have to start all over from level one and work your way up. This means you're starting a new game from scratch, even though the storyline itself takes over where the original game left off.